Question

Polystyrene can be made more rigid by copolymerizing styrene with divinylbenzene: How does the divinylbenzene make the copolymer more rigid?

Short answer

Divinylbenzene makes the copolymer more rigid by acting as a cross-linker between the polymer chains during copolymerization. This creates bridges between chains, restricting their movement and leading to an overall increased rigidity and strength in the copolymer compared to regular polystyrene.

Step-by-step solution

Understanding the structures of styrene and divinylbenzene

Styrene is an organic compound with the chemical formula C8H8. Its molecular structure consists of a vinyl group (C=C) attached to a phenyl ring (C6H5). Divinylbenzene, on the other hand, is an organic compound with two vinyl groups attached to a benzene ring. Its chemical formula is C10H10.

Copolymerization

Copolymerization is a chemical process in which two or more different types of monomers (i.e., styrene and divinylbenzene) are combined together to form a larger molecule, the polymer (copolymer). In this case, styrene and divinylbenzene are mixed, and the polymerization reaction is initiated to form a copolymer, which has both styrene and divinylbenzene units in its structure.

Cross-linking formation

One of the key aspects of copolymerization in this case is the formation of cross-links between the polymer chains. Due to the presence of two vinyl groups in the divinylbenzene molecule, it can act as a ''cross-linker'' between different polymer chains. During the polymerization process, one vinyl group from divinylbenzene reacts with a styrene unit to form a bond, while the other vinyl group can react with a different styrene unit, thus forming a bridge between two polymer chains.

Increased rigidity in the copolymer

The cross-links formed by the divinylbenzene molecules make the final copolymer more rigid. This is because cross-linking restricts the movement of the polymer chains, making it more difficult for them to slide past each other. The increased number of connections between the chains results in a more rigid structure, which then translates to the overall rigidity of the material. In conclusion, divinylbenzene makes polystyrene more rigid when copolymerized together because it acts as a cross-linker, forming bridges between the polymer chains and restricting their movement. This results in a more rigid and stronger copolymer with improved mechanical properties compared to regular polystyrene.